There has been an advancing tendency since 1990s in Japan with respect to a boiler toward high temperature and high pressure, and the current mainstream is an Ultra Super Critical power (USC) boiler for a steam temperature beyond 600° C.
In other areas of the world, including Europe or China, highly efficient USC boilers have been constructed one after another from the viewpoint of CO2 reduction as a global environmental countermeasure.
As a source material steel to be used for a heat exchanger tube to generate high temperature high pressure steam in a boiler, and for a pipe of a boiler, a steel material with superior high temperature strength has been demanded and various steel materials have been developed recently.
For example, Patent Literature 1 discloses, as a high Cr-based austenitic stainless steel, a high strength austenitic stainless steel superior in high temperature strength and suitable for a material of a chemical plant vessel using petroleum and coal as a fuel, a material of a heat exchanger, or a material of a high temperature component such as a boiler tube or a fast reactor.
Patent Literature 2 discloses an austenitic stainless steel pipe superior in creep rupture strength at a high temperature for a long time period, and suitable for a material to be used in a high temperature and high pressure environment, such as a steel tube or pipe for a boiler, or a high temperature pressure vessel.
Patent Literature 3 discloses a high temperature austenite stainless steel which is superior in workability after long term use and is suitable for a material for a steel tube or pipe to be used as a superheater pipe or a reheater pipe of a boiler, a reacting furnace pipe in a chemical plant, etc, or as a material for a steel plate, a steel bar, a steel forging, etc. to be used as a heat-resistant, and pressure-resistant component.
Patent Literature 4 discloses an austenite stainless steel, which is superior in high temperature corrosion thermal fatigue cracking resistance, is able to withstand an environment subjected to high temperature corrosion at 500° C. or higher as well as repeated thermal fatigue, and is suitable for a pipe, a plate, a bar, a forging, etc. to be used for a heat exchanger component of a HRSG (Heat Recovery Steam Generator) or a next-generation solar power generator, or a heat-resistant and pressure-resistant component for a power generation boiler, a chemical plant, an atomic power plant, etc.
Patent Literature 5 discloses a high strength austenite stainless steel which is superior in toughness after aging, is applicable to a high strength steel tube or pipe for a boiler, etc, and is usable for ultra-supercritical coal fired power generation, integrated coal gasification combined cycle power generation, etc.
Patent Literature 6 discloses a high strength austenite stainless steel to be used for ultra-supercritical coal fired power generation, integrated coal gasification combined cycle power generation, or the like.    Patent Literature 1: Japanese Patent No. 2510206    Patent Literature 2: Japanese Patent Application Laid-Open (JP-A) No. 2002-212634    Patent Literature 3: Japanese Patent No. 4946758    Patent Literature 4: Japanese Patent No. 5029788    Patent Literature 5: Japanese Patent No. 5661001    Patent Literature 6: Japanese Patent No. 5670103